This invention relates in general to an improved process, and more specifically, to an improved process for preparing squaraine compositions of matter.
Squaraine compositions are useful for incorporation into photoresponsive devices to extend the capability of such devices to be responsive to visible light as well as infrared illumination. These photoresponsive devices can therefore be utilized, for example, in conventional electrophotographic copiers as well as in laser printers. These photoresponsive devices may comprise single or multilayered members which employ photoconductive materials comprising squaraine compositions in a photogenerating layer, between a photogenerating layer and a hole transport layer, or between a photogenerating layer and a supporting substrate.
Photoconductive imaging members containing certain squaraine compositions, including amine derivatives of squaric acid, are known. Also known are layered photoresponsive devices containing photogenerating layers and transport layers, as described, for example in U.S. Pat. No. 4,123,270. Examples of photogenerating layer compositions disclosed in this patent include 2,4-bis-(2-methyl-4-dimethylamino-phenyl)-1,3-cyclobutadiene-diylium-1,3-d iolate, 2,4-bis-(2-hydroxy-4-dimethylamino-phenyl)-1,3-cyclobutadiene-diylium-1,3- diolate, and 2,4-bis-(p- dimethylamino-phenyl)-1,3-cyclobutadiene-diylium-1,3-diolate. Numerous photosensitive squaraine compositions are also disclosed in U.S. Pat. No. 3,824,099. Some of the squaraine compositions in this patent comprise tertiary amines.
In a copending application entitled Processes for the Preparation of Squaraine Compositions, U.S. Ser. No. 557,796, filed in the name of Kock Yee-Law concurrently herewith, a dialkyl squarate and a dialkyl aniline, in the presence of an acid catalyst, are reacted at a temperature of from about 80.degree. C. to 160.degree. C. Solvents, such as aliphatic alcohols, including methanol, ethanol, propanol, butanol, especially water saturated 1-butanol, amyl alcohol, are selected for the purpose of forming a solution of the squarate and the acid.
In a copending application entitled Novel Squaraine Systems, U.S. Ser. No. 557,795, filed in the name of John F. Yanus concurrently herewith, squaric acid, a first tertiary amine and a second tertiary amine different from the first tertiary amine are reacted in the presence of a long chain primary alcohol having a boiling point between about 130.degree. C. and about 210.degree. C. An acid catalyst may also be present during the reaction.
While the above processes for preparing squaraine compositions may be suitable for their intended purposes, there continues to be a need for other processes wherein novel squaraine compositions, useful as photoconductive materials, can be prepared with higher yields in less time. Additionally, there remains a need for simple, economical processes for preparing squaraine compositions wherein the resulting squaraine products exhibit excellent photoreceptor dark decay and photosensitivity properties.